adventurer Steve Fossett

(CNN) — The wife of missing adventurer Steve Fossett has asked a court to declare him dead.

Fossett was last seen in early September, flying a single-engine plane on a pleasure flight from a Nevada ranch. A month-long search for the plane was unsuccessful.

“As difficult as it is for me to reach this conclusion, I no longer hold out any hope that Steve has survived," wrote Peggy V. Fossett in court documents filed Monday with the Cook County [Illinois] Circuit Court.

She asked that the will of her husband of 38 years be admitted to probate.